Amyloidosis and the Accumulation of Beta-Amyloid Plaques in the Brain of a Variety of Disorders
Alzheimer's disease is characterized by the accumulation of a 39-43 amino acid peptide termed the beta-amyloid protein or AP, in a fibrillary form, existing as extracellular amyloid plaques and as amyloid within the walls of cerebral blood vessels. Fibrillar A13 amyloid deposition in Alzheimer's disease is believed to be detrimental to the patient and eventually leads to toxicity and neuronal cell death, a characteristic hallmark of Alzheimer's disease. Accumulating evidence implicates amyloid, and more specifically, the formation, deposition, accumulation and/or persistence of AP fibrils, as a major causative factor of Alzheimer's disease pathogenesis. In addition, besides Alzheimer's disease, a number of other amyloid diseases involve formation, deposition, accumulation and persistence of AP fibrils, including Down's syndrome, disorders involving congophilic angiopathy, such as but not limited to, hereditary cerebral hemorrhage of the Dutch type, inclusion body myositosis, dementia pugilistica, cerebral (3-amyloid angiopathy, dementia associated with progressive supranuclear palsy, dementia associated with cortical basal degeneration and mild cognitive impairment.
The amyloid diseases (amyloidosis) are classified according to the type of amyloid protein as well as the underlying disease. Amyloid diseases have a number of common characteristics including each amyloid consisting of a unique type of amyloid protein. The amyloid diseases include, but are not limited to, the amyloid associated with Alzheimer's disease, Down's syndrome, Canine Dysfunction syndrome (CDS), Canine Cognitive Dysfunction (CCD), as seen in aged animals such as dogs and cats, hereditary cerebral hemorrhage with amyloidosis of the Dutch type, dementia pugilistica, inclusion body myositosis (Askanas et al., Ann. Neurol. 43:521-560, 1993) and mild cognitive impairment (where the specific amyloid is referred to as beta-amyloid protein or Aβ), the amyloid associated with chronic inflammation, various forms of malignancy and Familial Mediterranean Fever (where the specific amyloid is referred to as AA amyloid or inflammation-associated amyloidosis), the amyloid associated with multiple myeloma and other B-cell dyscrasias (where the specific amyloid is referred to as AL amyloid), the amyloid associated with type 2 diabetes (where the specific amyloid is referred to as amylin or islet amyloid polypeptide or IAPP), the amyloid associated with the prion diseases including Creutzfeld-Jakob disease, Gerstamann-Straussler syndrome, kuru and animal scrapie (where the specific amyloid is referred to as PrP amyloid), the amyloid associated with long-term hemodialysis and carpal tunnel syndrome (where the specific amyloid is referred to as α2-microglobulin amyloid), the amyloid associated with senile cardiac amyloidosis and Familial Amyloidotic Polyneuropathy (where the specific amyloid is referred to as transthyretin or prealbumin), and the amyloid associated with endocrine tumors such as medullary carcinoma of the thyroid (where the specific amyloid is referred to as variants of procalcitonin). In addition, the α-synuclein protein which forms amyloid-like fibrils, and is Congo red and Thioflavin S positive (specific stains used to detect amyloid fibrillary deposits), is found as part of Lewy bodies in the brains of patients with Parkinson's disease, Lewy body disease (Lewy in Handbuch der Neurologie, M. Lewandowsld, ed., Springer, Berlin pp. 920-933, 1912; Pollanen et al, J. Neuropath, Exp. Neurol. 52:183-191, 1993; Spillantini et al, Proc. Natl. Acad. Sci. USA 95:6469-6473, 1998; Arai et. al, Neurosc, Lett. 259:83-86, 1999), multiple system atrophy (Wakabayashi et al, Acta Neuropath. 96:445-452, 1998), dementia with Lewy bodies, and the Lewy body variant of Alzheimer's disease. For purposes of this disclosure, Parkinson's disease, due to the fact that fibrils develop in the brains of patients with this disease (which are Congo red and Thioflavin S positive, and which contain predominant beta-pleated sheet secondary structure), is now regarded as a disease that also displays the characteristics of an amyloid-disease.
Amyloid as a Therapeutic Target for Alzheimer's Disease
Alzheimer's disease is characterized by the deposition and accumulation of a 39-43 amino acid peptide termed the beta-amyloid protein, Aβ or β/A4 (Glenner and Wong, Biochem. Biophys, Res, Comm. 120:885-890, 1984; Masters et al, Proc. Natl. Acad. Sci. USA 82:4245-4249, 1985; Husby et al, Bull, WHO 71:105-108, 1993), Aβ is derived by protease cleavage from larger precursor proteins termed β-amyloid precursor proteins. (APPs) of which there are several alternatively spliced variants. The most abundant forms of the APPs include proteins consisting of 696, 751 and 770 amino acids (Tanzi et al. Nature 31:528-530, 19980.
The small Aβ peptide is a major component that makes up the amyloid deposits or “plaques” in the brains of patients with Alzheimer's disease. In addition, Alzheimer's disease is characterized by the presence of numerous neurofibrillary “tangles”, consisting of paired helical filaments which abnormally accumulate in the neuronal cytoplasm (Grunddke-Iqbal et al, Proc. Natl. Acad. Sci. USA. 83:4913-4917, 1986; Kosik et al, Proc. Natl. Acad. Sci. USA 83:4044-4048, 1986; Lee et al, Science 251:675-678, 1991). The pathological hallmark of Alzheimer's disease is therefore the presence of both “plaques” and “tangles”, with amyloid being deposited in the central core of the plaques. The other major type of lesion found in the Alzheimer's disease brain is the accumulation of amyloid in the walls of blood vessels, both within the brain parenchyma and in the walls of meningeal vessels that lie outside the brain. The amyloid deposits localized to the walls of blood vessels are referred to as cerebrovascular amyloid or congophilic angiopathy (Mandybur, J. Neuropath. Exp. Neurol. 45:79-90, 1986; Pardridge et al., J. Neurochem, 49:1394-1401, 1987).
For many years there has been an ongoing scientific debate as to the importance of “amyloid” in Alzheimer's disease, and whether the “plaques” and “tangles” characteristic of this disease were a cause or merely a consequence of the disease. Within the last few years, studies now indicate that amyloid is indeed a causative factor for Alzheimer's disease and should not be regarded as merely an innocent bystander. The Alzheimer's Aβ protein in cell culture has been shown to cause degeneration of nerve cells within short periods of time (Pike et al, Br. Res. 563:311-314, 1991; J. Neurochem. 64:253-265, 1995). Studies show that it is the fibrillary structure (consisting of a predominant β-pleated sheet secondary structure) characteristic of all amyloids that is responsible for the neurotoxic effects, Aβ has also been found to be neurotoxic in slice cultures of hippocampus (Harrigan et al, Neurobiol. Aging 16:779-789, 1995) and to induce nerve cell death in transgenic mice (Games et. al, Nature 373:523-527, 1995; Hsiao et al, Science 272:99-102, 1996). Injection of the Alzheimer's Aβ into rat brain also causes memory impairment and neuronal dysfunction (Flood et al, Proc. Natl. Acad. Sci. USA 88:3363-3366, 1991; Br. Res. 663:271-276, 1994).
Probably, the most convincing evidence that Aβ amyloid is directly involved in the pathogenesis of Alzheimer's disease comes from genetic studies. It was discovered that the production of Aβ can result from mutations in the gene encoding its precursor, β-amyloid precursor protein (Van Broeckhoven et al, Science 248:1120-1122, 1990; Murrell et al, Science 254:97-99, 1991; Haass et al, Nature Med. 1:1291-1296, 1995). The identification of mutations in the beta-amyloid precursor protein gene that cause early onset familial Alzheimer's disease is the strongest argument that amyloid is central to the pathogenic process underlying this diseases. Several reported disease-causing mutations have been discovered which demonstrate the importance of Aβ in causing familial Alzheimer's disease (reviewed in Hardy, Nature Genet. 1:223-234, 1992). All of these studies suggest that providing a therapy, drug or supplement to reduce, eliminate and/or prevent fibrillary Aβ formation, deposition, accumulation and/or persistence in the brains of humans and animals, well serve as an effective therapeutic.
The Accumulation of “Plaques and Tangles” in the Aging Human and Animal Brain
The human brain is the most complex organ in the universe. It weighs only 3 pounds, or about 2% of body weight. Yet is uses 20-30% of the calories consumed, 20% of the oxygen breathed, and 25% of the blood flow in the body; it consists of 85% water (Daniel G. Amen, M.D. 12 prescriptions for creating a brain healthy life. Source: www.amenclinics.com/cybcyb/12-prescriptions-for-creating-a-brain-healthy-life/). There are approximately 100 billion nerve cells (i.e. neurons) in the brain, and up to a quadrillion connections called synapses (ibid). The human brain as it ages, loses about 85,000 cortical neurons per day, or about one every second (Deepak Chopra, M.D. and Rudolph Tanzi, Ph.D. Super Brain. Unleashing the Explosive Power of Your Mind to Maximize Health, Happiness, and Spiritual Well Being. See///www.chopra.com/super-brain-by-deepak-chopra-rudolph-tanzi.) As the brain ages, starting in the 20's there is a slow but deliberate accumulation of two neurotoxic proteins. The first is the brain accumulation of an insoluble (aggregated) specific neurotoxic protein known as the “beta-amyloid protein” or Aβ. Beta-amyloid protein deposits in the form of “plaques” (looking like “meatballs” in the brain under a microscope), have been shown to be instrumental in killing healthy neurons that lead to a decline in hippocampus-dependent memory and cognition. Dr. Alan Snow and co-inventors developed patented methods to produce “plaques in a test-tube” (identical to what is seen in the human brain) and used these methods to screen for and identify natural “plaque-reducing” nutraceutical ingredients (U.S. Pat. No. 7,148,001, which is incorporated herein by reference in its entirety).
The second neurotoxic protein that accumulates in the aging brain is known as the “tau protein” and forms twisted paired helical filaments known as “tangles.” Neurofibrillary tangles accumulate inside neurons that causes them to die, and look like “dried spaghetti strands” under a microscope. Dr. Snow's laboratories developed proprietary methods to form “tangles” in a test-tube, and then used these assays to identify “tangle-inhibiting” nutraceutical ingredients (see examples below). Thus, in the aging brain, both “plaques and tangles” accumulate, causing neurons to die; connections between nerve cells (called synapses) to disintegrate; and memory and cognition to progressively decline. Compounds or agents able to disaggregate and reduce the accumulation of “plaques and tangles” have been shown to lead to memory improvement and a reduction in memory decline (Karlnoski et al. Suppression of amyloid deposition leads to long-term reductions in Alzheimer's pathologies in Tg2576 mice. J. Neurosc. 29:4964-4971, 2009; Vellas et al. Long-term follow-up of patients immunized with AN1792: Reduced functional decline in antibody responders. Current Alz. Res. 6:144-151, 2009; Morgan et al, Aβ peptide vaccination prevents memory loss in an animal model of Alzheimer's disease. Nature 408:982-985, 2000; Chen et al. A. learning deficit related to age and β-amyloid plaques in a mouse model of Alzheimer's disease. Nature 408:975-979, 2000; Janus et al. Aβ peptide immunization reduces behavioral impairment and plaques in a model of Alzheimer's disease. Nature 408:979-985, 2000; Schenk et al. Immunization with amyloid-β attenuates Alzheimer-disease like pathology in PDAPP mouse. Nature 400:173-177, 1999; Yanamandra et al. Anti-tau antibodies that block tau aggregate seeding in vitro markedly decreases pathology and improves cognition in vivo. Neuron 80:402-414, 2013; Dumont et al. Bezafibrate administration improves behavioral deficits and tau pathology in P3015 mice. Human Molecular Genetics 21:5091-5105, 2012; Oddo et al. Reduction of soluble Abeta and tau, but not soluble Abeta alone, ameliorates cognitive decline in transgenic mice with plaques and tangles. J. Biol. Chem. 281:39413-39423, 2006; Santacruz et al. Tau suppression in a neurodegenerative mouse model improves memory function. Science 309:476-481, 2005.)
The only difference between an aging brain that could lead to age-associated memory impairment (AAMI), then to mild-cognitive impairment (MCI), and potentially to Alzheimer's disease, and a brain that does not, is the number of “plaques and tangles” in the brain. Alzheimer's diseased brains are loaded with tens to hundreds of thousands of “plaques and tangles,” per square millimeter, causing a marked increase in the death of neurons, leading to a loss of synapses (connections between neurons), and concurrent memory loss and cognitive decline.
Therefore, beta-amyloid and tau are two key proteins in the aging brain that accumulate as insoluble “plaques and tangles” that have been shown to be directly linked to memory loss and cognitive decline. There is currently no pharmaceutical drug that has been approved for reducing and removing both beta-amyloid protein “plaques” and tau protein-containing “tangles” in the brain.
The Accumulation of “Plaques” in the Aging Dog and Cat Brain
Dogs and cats also accumulate “plaques” (and, to a lesser extent, “tangles”) in their brains as they age that are believed to contribute to memory decline and cognitive impairment. The same beta-amyloid protein (i.e. “plaques”) and tau protein (“tangles”) that accumulate in the human brain also accumulate in aged dogs (Papoiannou et al, Immunohistochemical investigation of the brain of aged dogs. I. Detection of neurofibrillary tangles and of 4-hydroxynonenal protein, an oxidative damage product, in senile plaques. Amyloid 8:11-21, 2001; Uchida et al, Amyloid angiopathy with cerebral hemorrhage and senile plaque in aged dogs. Nihon Juigaku Zasshi 52: 605-11, 1990) and cats (Gunn-Moore et al, Cognitive dysfunction and the neurobiology of ageing in cats. J Small Anim. Pract. 48: 546-53, 2007; Nakamura et al. Senile plaques in very aged cats. Acta Neuropath. 91:437-9, 1996).
Canine Cognitive Dysfunction (CCD) (also known as Cognitive Dysfunction Syndrome or CDS) is a disease prevalent in dogs (and cats) that exhibit symptoms of dementia or Alzheimer's disease as seen in humans. CCD creates pathological changes in the brain that slow the mental functioning of dogs (and cats) resulting in loss of memory, motor function and learned behaviors from training early in life. In the dog's and cat's brain, the culprit is again is the beta-amyloid protein or Aβ that forms “plaques” in the brain. As the dog ages, more and more “plaques” accumulate and nerve cells die. Although the initial symptoms of the disorders are mild, they gradually worsen over time, also known as “cognitive decline”. Amyloid “plaques” occur in aged dogs at about five to seven years of age, and in cats of about ten years of age (which is proportional to their average lifespan of 15-20 years). In fact, clinical signs of cognitive dysfunction syndrome are found in 50% of dogs over the age of 11, and by the age of 15, 68% of dogs display at least one sign. Dogs will often find themselves confused in familiar places of the home, spending long periods of time in one area of the home, not responding to calls or commands, and experiencing abnormal sleeping patterns.
Beta-amyloid protein containing “plaques” also have been identified in the brains of other higher mammals including monkeys, bears, camels, and horses, (Nakamura et al, Histopathological studies of senile plaques and cerebral amyloidosis in cynomolgus monkeys. J Med Primatol. 27:244-52, 1998; Capucchio et al studies. J Comp Pathol 142:61-73, 2010; Nakamura et al, Senile plaques in an aged two-humped (Bactrian) camel (Camelus bactrianus), Acta Neuropathol 90: 415-8, 1995; Uchida et al. Senile plaques and other senile changes in the brain of an aged American black bear, Vet. Pathol. 32:412-4, 1995).
Tauopathies and “Tangles”
Tau was discovered in the mid-1970s as a microtubule associated protein (Weingarten, 1975). Besides being a stabilizer of microtubules in neurons and other cells, it has since been found to play important roles in cell differentiation, polarization and axonal transport. Normal tau is a soluble protein bound to microtubules, but in a series of neurodegenerative diseases, now known as tauopathies, tau accumulates as a pathogenic insoluble, fibrillar protein. These tau inclusions appear to modulate the severity of dementia and clinical features of these neurodegenerative diseases. Tauopathies include diseases such as Alzheimer's disease, frontotemporal lobar degeneration with tau inclusions (FTLD-tau) such as Pick's disease, progressive supranuclear palsy, and corticobasal degeneration, agyropbillic grain disease, some prion diseases, amyotrophic lateral sclerosis/parkinsonism-dementia complex, chrome traumatic encephalopathy, and some genetic forms of Parkinson's disease (V. M. Lee et al., Ann. Rev. Neurosci. 24:1121-1159, 2001; B. Omalu et al., Neurosurgery 69(1): 173-83, 2011; A. Rajput et al., Neurology 67:1506-1508, 2006; G. Santpere and I. Ferrer, Acta Neuropathol. 117: 227-246, 2009).
One of the most notable effects of increasing fibrillar tau in the brain is the gradual deterioration of short term memory; that is, the ability to recall immediately those memories only recently stored (P. Giannakopoulos et al., Neurology 60:1495-1500, 2003). As there is no treatment for these disorders, it is important to find a novel invention that could target this pathogenic protein and improve memory deficits.
“Tangles” Accumulate in Brain in Traumatic Brain Injury (TBI), Concussions, Head Trauma and Chronic Traumatic Encephalopathy (CTE)
Brain “tangles” consisting of tau protein also accumulate progressively in the brain following blows to the head and include concussions, head injury, post-traumatic stress disorder (PTSD), and blast-induced traumatic brain injury (seen in soldiers and military personnel who have traumatic head injuries induced by a single blast). The movie “concussion” and the NFL Players Association all discuss the dementia-type behavior that has been seen in athletes following repealed concussions and/or blows to the head (known as traumatic brain injury or TBI). Loss of consciousness is a clinical hallmark of concussion but is not required to make the diagnosis. Other symptoms include confusion, disorientation, unsteadiness, dizziness, headache, and visual disturbances.
The long-term consequences to traumatic brain injury is referred to as Chronic Traumatic Encephalopathy (CTE), which is form of tauopathy (i.e. tau protein containing “tangles” in the brain). CTE is a progressive degenerative disease found in people who have suffered repeated brain trauma including sub-concussive hits to the head that do not cause immediate symptoms. The disease was previously called dementia pugilistica (DP), i.e. “punch-drunk” as it was initially found in those with a history of boxing. CTE has now been found in the brains of professional athletes including NFL athletes who play football, athletes prone to head injury including those that play ice hockey, rugby, skiing, skateboarding, stunt performing, bull riding, rodeo, and all other contact sports where participants experience repeated brain trauma. Individuals with CTE show many signs of dementia such as memory loss, aggression, confusion, and depression, which may appear years or many decades after the trauma. In September 2015, researchers with the Department of Veterans Affairs and Boston University announced they had identified CTE in 96% of NFL football players that they had examined and in 79% of all football players (Jason Breslow, New; 87 deceased NFL players test positive for brain disease. Frontline Jan. 9, 2016).
The neuropathology under a microscope is clear—there is primarily an accumulation of “tangles” that consist of tau protein, similar to the “tangles” seen in the brains of Alzheimer's disease patients. There is also some beta-amyloid protein deposition (i.e. “plaques”), but this is usually uncommon and less of a feature then the “tangle” accumulation in brain. These findings suggest that blows to the head can lead to near immediate brain “tangle” accumulation that then leads to dementia-like symptoms including memory loss and cognitive decline. Identification of a nutraceutical that can help in the reduction and/or clearance of brain “tangles” would be an extraordinary supplement to take every day by all kinds of athletes, NFL players, the military and its soldiers.